I need a method, that opens the passed url in Android's browser. Like opennng a like in Windows would open the default browser in windows. I also need to program in an alert that would confirm they want to quit the app.

Nobody is going to write your code for you. What you are trying to do is not impossible, but you have a lot to learn about Java, Objective C, iPhone development and Android development before you tackle it. This is not the kind of project you can dive into the middle of and learn as you go. Work through some tutorials and do some small projects on each platform before you attempt this.